The present invention relates to a seat reclining mechanism for adjusting an angle of inclination of a seat back with respect to a seat cushion.
A vehicular seat reclining mechanism of this kind is known and disclosed for example in Japanese Patent Laid-Open Publication No. Hei 8-52040 (1996).
This vehicular seat reclining mechanism includes a lower arm adapted to be secured on a seat cushion, an upper arm adapted to be secured on a seat back and turnably connected with the lower arm, the upper arm having a ratchet, further, a pawl interposed between opposed surfaces of the lower arm and the upper arm and slidable along guide wall means formed on the lower arm to engage with or disengage from the ratchet, a cam member interposed between said opposed surfaces and engageable with the pawl to push the pawl in the direction for meshing with the ratchet, and a handle supported on a shaft passing through both the arms and capable of rotation of the cam member when it is operated.
In this mechanism of the prior art, the pawl is forced to be moved into meshing engagement with the ratchet by the cam member, and the turns of the upper arm with respect to the lower arm are regulated by guiding and supporting the pawl by the guide wall means. But, the upper arm is turned with respect to the lower arm by sliding the pawl along the guide wall means to release the meshing engagement with the ratchet.
In this conventional device, on the other hand, in order to improve the strength in the turn regulation of the upper arm with respect to the lower arm, regulating teeth to mesh with the pawl are additionally formed on the lower arm so that a high load to be applied to the upper arm may be ensured by assist of the meshing engagement between the pawl and the additional regulating teeth.
In the conventional device thus constructed, however, since the regulating teeth mesh with the pawl, a size management of high accuracy is required to form the additional regulating teeth and has to be performed not to influence the meshing engagement between the ratchet and the pawl, thereby to cause a rise in the cost. On the other hand, it is difficult to suppress the inclination of the pawl intentionally when the high load is applied to the upper arm. The disengagement between the ratchet and the pawl may be caused by the floating of the pawl, as caused by a deformation of the guide wall means.